Radio communication apparatus, radio communication system, and radio communication method

ABSTRACT

A radio communication apparatus to perform communication with another radio communication apparatus by using a plurality of frequency bands, the radio communication apparatus includes, a receiving unit configured to receive, when performing a random access procedure to said another radio communication apparatus, a control message by using a first frequency band as a response to a preamble message transmitted by the radio communication apparatus, the control message instructing communication using a second frequency band different from the first frequency band; and a control unit configured to perform, when the control message corresponds to the preamble message, data communication with said another radio communication apparatus by using the second frequency band.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 14/529,898, filed on Oct. 31, 2014, now pending,which is a continuation of U.S. patent application Ser. No. 14/268,214,filed on May 2, 2014, now U.S. Pat. No. 8,902,847, issued Dec. 2, 2014,which is a continuation of U.S. patent application Ser. No. 13/567,500filed on Aug. 6, 2012, now U.S. Pat. No. 8,780,855, issued Jul. 15,2014, which claims priority to International ApplicationPCT/JP2010/052103, filed on Feb. 12, 2010, the entire contents of eachare incorporated herein by reference.

FIELD

The embodiment discussed herein is related to a radio communicationapparatus, a radio communication system, and a radio communicationmethod.

BACKGROUND

A plurality of radio communication systems such as a cell-phone systemand a radio MAN (Metropolitan Area Network) are currently used. Forattaining a further speeding up and large capacity of radiocommunication, lively discussion is continuously performed about a nextgeneration radio communication technology.

For example, in a 3GPP (3rd Generation Partnership Project) being astandardization organization, there is proposed a communication standardreferred to as an LTE (Long Term Evolution) enabling communication usinga frequency band of 20 MHz at a maximum. Further, as a next generationcommunication standard of LTE, there is proposed a communicationstandard referred to as an LTE-A (LTE-Advanced) enabling communicationusing five frequency bands (namely, a frequency band of 100 MHz) of 20MHz at a maximum (see, for example, Non-Patent Literatures 1 and 2). Inthe LTE-A, the number of frequency bands to be used is proposed to bedynamically changed according to traffic (see, for example, Non-PatentLiterature 3).

Further, in a radio communication system, from one radio communicationdevice (e.g., a mobile station) to another radio communication device(e.g., a base station) which performs allocation control of radioresources, a random access may be performed. The random access from themobile station to the base station is performed, for example, at thetime when (1) the mobile station first accesses the base station, (2) anallocation of radio resources used for data transmission is requested tothe base station, and (3) synchronization is established duringreception of data from the base station, and (4) synchronization isachieved with a mobile target base station during a handover.

The random access includes a contention based random access and anon-contention based random access (see, for example, 10. 1. 5 sectionof Non-Patent Literature 4, and 5. 1 section of Non-Patent Literature5). In the case of the random access from the mobile station to the basestation, in the contention based random access, the mobile stationarbitrarily selects a signal sequence from among a plurality of signalsequences and transmits it to the base station as a random accesspreamble. In the non-contention based random access, the base stationnotifies the mobile station of information in which a signal sequence isspecified and the mobile station transmits a signal sequence accordingto the notification from the base station as the random access preamble.

-   NPTL1: 3GPP (3rd Generation Partnership Project), “Requirements for    further advancements for Evolved Universal Terrestrial Radio Access    (E-UTRA) (LTE-Advanced)”, 3GPP TR 36.913 V8.0.1, 2009-03.-   NPTL2: 3GPP (3rd Generation Partnership Project), “Feasibility study    for Further Advancements for E-UTRA (LTE-Advanced)”, 3GPP TR 36.912    V9.0.0, 2009-09.-   NPTL3: 3GPP (3rd Generation Partnership Project), “The need for    additional activation procedure in carrier aggregation”, 3GPP    TSG-RAN WG2 #67bis R2-095874, 2009-10.-   NPTL4: 3GPP (3rd Generation Partnership Project), “Evolved Universal    Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial    Radio Access Network (E-UTRAN); Overall description”, 3GPP TS 36.300    V9.0.0, 2009-06.-   NPTL5: 3GPP (3rd Generation Partnership Project), “Evolved Universal    Terrestrial Radio Access (E-UTRA) Medium Access Control (MAC)    protocol specification”, 3GPP TS 36.321 V9.1.0, 2009-12.

Incidentally, in a radio communication system capable of performingcommunication by using a plurality of frequency bands, the number offrequency bands to be used according to traffic as described above isconsidered to be changed. However, in a method as described in theNon-Patent Literature 3, after communication is started between radiocommunication devices (after completing a random access procedure), aprocedure is freshly performed so as to use other frequency bands exceptthe frequency band in which communication is started. In this method, inthe case where it is proved that the other frequency bands are desiredto be used before starting communication (for example, in the case wherea transmission data amount is proved to be large), the procedure becomesinefficient.

SUMMARY

According to an aspect of the embodiments, there is provided a radiocommunication apparatus to perform communication with another radiocommunication apparatus by using a plurality of frequency bands. Theapparatus includes: a receiving unit configured to receive by using afirst frequency band a control message including identificationinformation indicating a second frequency band different from the firstfrequency band during a random access procedure to said another radiocommunication apparatus; and a control unit configured to control datacommunication between said another radio communication apparatus and theradio communication apparatus by using the second frequency bandindicated by the identification information included in the controlmessage.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 illustrates a radio communication system according to a firstembodiment,

FIG. 2 illustrates a mobile communication system according to a secondembodiment,

FIG. 3 is a sequence diagram illustrating a contention based randomaccess procedure,

FIG. 4 is a sequence diagram illustrating a non-contention based randomaccess procedure,

FIG. 5 illustrates a component carrier in which radio communication isperformed,

FIG. 6 is a block diagram illustrating a base station,

FIG. 7 is a block diagram illustrating a mobile station,

FIG. 8 is a flowchart illustrating a process of a base station accordingto a second embodiment,

FIG. 9 is a flowchart illustrating a process of a mobile stationaccording to a second embodiment,

FIG. 10 illustrates a first random access example according to a secondembodiment,

FIG. 11 illustrates a second random access example according to a secondembodiment,

FIG. 12 illustrates a third random access example according to a secondembodiment,

FIG. 13 illustrates a first format example of a Msg0,

FIG. 14 illustrates a second format example of a Msg0,

FIG. 15 illustrates a third format example of a Msg0,

FIG. 16 illustrates a first size adjustment example of a Msg0,

FIG. 17 illustrates a second size adjustment example of a Msg0,

FIG. 18 illustrates a third size adjustment example of a Msg0,

FIG. 19 is a flowchart illustrating a process of a base stationaccording to a third embodiment,

FIG. 20 is a flowchart illustrating a process of a mobile stationaccording to a third embodiment,

FIG. 21 illustrates a first random access example according to a thirdembodiment,

FIG. 22 illustrates a second random access example according to a thirdembodiment,

FIG. 23 illustrates a third random access example according to a thirdembodiment,

FIG. 24 illustrates a first format example of a Msg2,

FIG. 25 illustrates a second format example of a Msg2,

FIG. 26 illustrates a third format example of a Msg2,

FIG. 27 is a flowchart illustrating a process of a base stationaccording to a fourth embodiment,

FIG. 28 is a flowchart illustrating a process of a mobile stationaccording to a fourth embodiment,

FIG. 29 illustrates a first random access example according to a fourthembodiment,

FIG. 30 illustrates a second random access example according to a fourthembodiment, and

FIG. 31 illustrates a third random access example according to a fourthembodiment.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will now be described indetail below with reference to the accompanying drawings, wherein likereference numerals refer to like elements throughout.

First Embodiment

FIG. 1 illustrates a radio communication system according to a firstembodiment. The radio communication system according to the firstembodiment includes radio communication apparatus 1 and 2. The radiocommunication apparatus 1 and 2 perform communication by using aplurality of frequency bands. Such a radio communication system isimplemented, for example, as an LTE-A system. In the LTE-A system, theplurality of frequency bands may be each referred to as a CC (ComponentCarrier).

The radio communication apparatus 1 performs allocation control of radioresources. Under the control of the radio communication apparatus 1, theradio communication apparatus 2 performs data communication between theradio communication apparatus 1 (or, another radio communicationapparatus) and its own apparatus. For example, the radio communicationapparatus 1 is implemented as a base station or a relay station, and theradio communication apparatus 2 is implemented as a subscriber station.Or, alternatively, the radio communication apparatus 1 may beimplemented as a base station, and the radio communication apparatus 2may be implemented as a relay station. The radio communication apparatus1 and 2 may be a fixed radio communication apparatus or a mobile radiocommunication apparatus.

The radio communication apparatus 1 has a control unit 1 a and atransmitting unit 1 b. The control unit 1 a sets a frequency band #1 asa frequency band used for a random access procedure through the radiocommunication apparatus 2. The control unit 1 a further selects afrequency band #2 as a frequency band used for data communicationthrough the radio communication apparatus 2. The transmitting unit 1 btransmits a control message relating to the random access to the radiocommunication apparatus 2 by using the frequency band #1. Into thiscontrol message, identification information indicating the frequencyband #2 is inserted. The identification information (e.g., a uniquenumber) is previously matched with the plurality of the frequency bands,respectively.

The radio communication apparatus 2 has a receiving unit 2 a and acontrol unit 2 b. The receiving unit 2 a receives the control messagerelating to the random access from the radio communication apparatus 1by using the frequency band #1. The control unit 2 b confirmsidentification information included in the received control message andcontrols the radio communication apparatus 2 to perform datacommunication by using the frequency band #2 indicated by theidentification information. Examples of the random access target anddata communication partner of the radio communication apparatus 1include the radio communication apparatus 1. Note that in the case ofperforming a handover from the radio communication apparatus 1 toanother radio communication apparatus, the random access target and datacommunication partner is a radio communication apparatus as a handovertarget.

As described above, as the random access, the radio communicationapparatus 2 performs the non-contention based random access orcontention based random access. In the case of the non-contention basedrandom access, for example, a message (Msg0) for specifying a signalsequence of a random access preamble or a random access response (Msg2)as a response for the random access preamble (Msg1) is considered to beused as the control message. In the case of the contention based randomaccess, the random access response is considered to be used as thecontrol message.

When receiving the control message including the identificationinformation by using the frequency band #1, the radio communicationapparatus 2 may continue a subsequent random access procedure by usingthe frequency band #2. In the case where the frequency band #2 is in ade-active state, at the time when receiving the control messageincluding the identification information, the radio communicationapparatus 2 may change a state of the frequency band #2 into an activestate. On the other hand, at the time when receiving the control messageincluding the identification information, the radio communicationapparatus 1 may change a state of the frequency band #2 into an activestate. In this case, the radio communication apparatus 1 and 2 need notseparately transmit and receive the control message for changing a stateof the frequency band #2 into an active state.

In the above-described radio communication system according to the firstembodiment, the radio communication apparatus 1 selects the frequencyband #2 as a frequency band used for data communication through theradio communication apparatus 2. At the time of performing the randomaccess procedure, by using the frequency band #1, the radiocommunication apparatus 1 transmits the control message including theidentification information indicating the frequency band #2 to the radiocommunication apparatus 2. On the other hand, at the time of performingthe random access procedure, by using the frequency band #1, the radiocommunication apparatus 2 receives the control message including theidentification information indicating the frequency band #2 from theradio communication apparatus 1. The radio communication apparatus 1then performs data communication by using the frequency band #2indicated by the identification information.

This process permits the radio communication apparatus to give apermission of the use of the frequency band #2 different from thefrequency band #1 used at the time of starting the random accessprocedure to the radio communication apparatus 2 during the randomaccess procedure. That is, the radio communication apparatus 1implements cross carrier scheduling during the random access procedure.Accordingly, after the random access procedure, the radio communicationapparatus 1 need not separately perform a procedure for giving apermission of the use of the frequency band #2 to the radiocommunication apparatus 2, and effectively performs the use control ofthe plurality of the frequency bands.

In the second to fourth embodiments, a case where the radiocommunication method according to the first embodiment is applied to amobile communication system of the LTE-A will be further described indetail below. Note that the radio communication method according to thefirst embodiment is applicable to the mobile communication system usinga communication method other than the LTE-A or the fixed radiocommunication system.

Second Embodiment

FIG. 2 illustrates a mobile communication system according to a secondembodiment. The mobile communication system according to the secondembodiment includes a base station 10, a mobile station 20, and a relaystation 30. This mobile communication system allows radio communicationusing five component carriers at a maximum.

The base station 10 is a radio communication apparatus which performscommunication directly with the mobile station 20 or via the relaystation 30. The base station 10 is connected to a host station (notillustrated) by wire, and transfers user data between a wired sectionand a radio section. The base station 10 manages radio resources of alink between the base station 10 and the mobile station 20, and furtherradio resources of a link between the base station 10 and the relaystation 30.

The mobile station 20 is a radio terminal device which accesses the basestation 10 or the relay station 30 and performs radio communication. Asthe mobile station 20, for example, a mobile phone handset device orportable information terminal device is used. The mobile station 20performs random access and establishes synchronization to the basestation 10 or the relay station 30, and then transmits and receivesdata.

The relay station 30 is a radio communication device which relays datatransmission between the base station 10 and the mobile station 20. Therelay station 30 may be a fixed communication device or a mobilecommunication device. The relay station 30 may perform random access tothe base station 10 and establish synchronization therewith. Inaddition, the relay station 30 manages radio resources of a link betweenthe relay station 30 and the mobile station 20.

In the following description of the second embodiment, the random accessprocedure performed between the base station 10 and the mobile station20 will be described. Even between the base station 10 and the relaystation 30 as well as between the relay station 30 and the mobilestation 20, the same random access procedure is performed.

FIG. 3 is a sequence diagram illustrating the contention based randomaccess procedure. The following section will now discuss the case wherethe random access procedure is performed in only one component carrier.The sequence illustrated in FIG. 3 includes the following steps:

(Step S11) When data to be transmitted in an UL (uplink) is generated,the mobile station 20 selects one arbitrary signal sequence from among aplurality of previously defined signal sequences. The mobile station 20then transmits a random access preamble (Msg1) including the selectedsignal sequence to the base station 10 by using a PRACH (Physical RandomAccess Channel). At this time, on the PRACH, a plurality of the mobilestations may transmit the Msg1 of the same signal sequence, namely,contention of the random access may be caused.

(Step S12) When detecting the Msg1 on the PRACH, the base station 10measures UL transmission timing of the mobile station 20, and at thesame time allocates a UL radio resource to the mobile station 20. Thebase station 10 then transmits the random access response (Msg2)including information for synchronizing the UL timing or informationindicating the allocated UL radio resource. In the case where thecontention of the random access is caused, the mobile stations whichtransmit the Msg1 receive the Msg2, respectively.

(Step S13) When receiving the Msg2, the mobile station 20 transmits ascheduled transmission (Msg3) including the identification informationof the mobile station 20 to the base station 10 by using the UL radioresource allocated by the base station 10. In the case where thecontention of the random access is caused, the mobile stations whichtransmit the Msg1 (namely, receive the Msg2) transmit an Msg3,respectively. In this case, a plurality of the transmitted Msg3 setsinterfere with each other on the same radio resource.

(Step S14) The base station 10 detects the Msg3 on the UL radio resourceallocated at step S12. Based on the identification information includedin the Msg3, the base station 10 recognizes the mobile station 20 whichperforms the random access. As a result, the base station 10 transmits acontention resolution (Msg4) indicating that the mobile station 20 isrecognized to the mobile station 20. The mobile station 20 thenestablishes synchronization between the base station 10 and its ownstation, and allows the data communication.

Note that in the case where the contention of the random access iscaused, the identification information of the mobile station as atransmission source fails to be extracted from the Msg3. In this case,the base station 10 transmits a message indicating that the contentionof the random access is caused. After waiting for only the random time,the mobile station 20 which receives the message returns to step S11 andperforms the random access procedure again. When the contention iseliminated, the mobile station 20 establishes synchronization betweenthe base station 10 and its own station, and allows the datacommunication.

FIG. 4 is a sequence diagram illustrating the non-contention basedrandom access procedure. The following section will now discuss the casewhere the random access procedure is performed in only one componentcarrier. The sequence illustrated in FIG. 4 includes the followingsteps:

(Step S21) When data transmitted in the downlink (DL) reaches the basestation 10, the base station 10 selects one unused signal sequence fromamong a plurality of the previously defined signal sequences. The basestation 10 then transmits the dedicated preamble notification (Msg0) forspecifying the selected signal sequence to the mobile station 20. Atthis time, the base station 10 performs exclusion control to a pluralityof mobile stations so as not to allocate the same signal sequence at thesame time.

(Step S22) Within the specified period (period of validity) fromreceiving the Msg0, the mobile station 20 transmits the Msg1 includingthe signal sequence specified by the Msg0 to the base station 10 byusing the PRACH. Here, since the specified signal sequence isexclusively allocated to the mobile stations 20 within the period ofvalidity, the contention of the random access is not caused.

(Step S23) When detecting the Msg1 on the PRACH, the base station 10allocates the UL radio resource to the mobile stations 20. The basestation 10 then transmits the Msg2 including information indicating theallocated UL radio resource to the mobile station 20. The datacommunication is then enabled between the base station 10 and the mobilestation 20. Since the contention of the random access is not caused, thebase station 10 need not transmit and receive the Msg3 and the Msg4 inthe non-contention based random access.

The contention based random access is performed, for example, at thetime when (1) the mobile station 20 first accesses the base station 10,and at the time when (2) the mobile station 20 requests the allocationof radio resources to the base station 10. The non-contention basedrandom access is performed, for example, (3) when receiving data fromthe base station 10, at the time when the mobile station 20 establishessynchronization with the base station 10, and (4) when performinghandover to the base station 10 from another base station, at the timewhen the mobile station 20 establishes synchronization with the basestation 10.

Note that when the non-contention based random access is to be performed(for example, at the time of establishing synchronization during thehandover or when the mobile station 20 receives data from the basestation 10) in the case where the separately allocated signal sequenceis exhausted in the base station 10, the Msg0 not including a dedicatedpreamble is transmitted and received. In this case, the contention basedrandom access is performed. In the case of the handover, the basestation 10 before the handover transmits the Msg0 to the mobile station20. According to the second embodiment, the base station 10 and themobile station 20 are supposed to perform the non-contention basedrandom access procedure.

FIG. 5 illustrates a component carrier in which the radio communicationis performed. As described above, the base station 10 and the mobilestation 20 use five component carriers (CC#1 to #5) at a maximum,thereby performing radio communication. All bandwidths of the CC#1 to #5may be the same as each other or different from each other.

To the CC#1 to #5, a CI (Carrier Indicator) of 3 bits is given asidentification information, respectively. Here, 0b000 (0) indicates theCC#1, 0b001 (1) indicates the CC#2, 0b010 (2) indicates the CC#3, 0b011(3) indicates the CC#4, and 0b100 (4) indicates the CC#5. Here, 0b101(5) and 0b110 (6) are unused values (reservation values). As describedlater, 0b111 (7) may be used for indicating its own component carrier.

The base station 10 sets their states of the CC#1 to #5 in each mobilestation. Based on the states of the CC#1 to #5, the mobile station 20controls radio reception processing of each component carrier. Based ontheir states, for example, the CC#1 to #5 are classified into“Configured but Deactivated CC”, “Configured and Activated CC”, and“PDCCH monitoring set”.

The “Configured but Deactivated CC” is a component carrier in which thedata communication is not currently performed and which is in a usablestate (de-active state). In the component carrier in a de-active state,the mobile station 20 need not monitor any of a PDCCH (Physical DownlinkControl CHannel) in which control data is transmitted and a PDSCH(Physical Downlink Shared CHannel) in which a data signal istransmitted. Namely, the mobile station 20 may stop the radio receptionprocessing of the frequency band.

The “Configured and Activated CC” is a component carrier (in an activestate) in which the data communication is currently performed. By usingthe component carrier in an active state, the mobile station 20 performsat least radio reception processing relating to the PDSCH to the mobilestation 20.

The “PDCCH monitoring set” is in an active state and a set of thecomponent carriers in which the PDCCH to the mobile station 20 may beset. The mobile station 20 monitors the PDCCH by using the componentcarriers included in this set. In the case where a signal length of thePDCCH is not constant, the mobile station 20 blind-decodes the PDCCH.Specifically, the mobile station 20 tries a plurality of decodesaccording to a length of available signal, thus extracting control data.Note that the “PDCCH monitoring set” is defined as a subset of the“Configured and Activated CC” and the reception processing of the PDCCHought to be performed by all of the “Configured and Activated CCs” insome cases. In this case, the “PDCCH monitoring set” and the “Configuredand Activated CC” mean the same set.

In addition, a component carrier in which the PDCCH is set may bedifferent in each mobile station. The base station 10 may set a part ofthe CC#1 to #5 as an ACC (Anchor-Component Carrier). The ACC is acomponent carrier to be monitored by the mobile station. In the casewhere the ACC is set, the ACC is included at least in the “PDCCHmonitoring set”. A component carrier set as the ACC may be specified ineach cell, or in each mobile station.

For performing two-way communication, the base station 10 and the mobilestation 20 may use TDD (Time Division Duplex) or FDD (Frequency DivisionDuplex). In the case where the TDD is used, one frequency band is setfor each CC. In the case where the FDD is used, a pair of a frequencyband for UL and a frequency band for DL is set for each CC. With regardto the after-mentioned random access procedure, any of the case where afrequency band is divided into the frequency band for UL and thefrequency band for DL and the case where a frequency band is not dividedinto the frequency band for UL and the frequency band for DL may beperformed.

FIG. 6 is a block diagram illustrating the base station. The basestation 10 has a radio communication unit 11, a scheduler 12, a wiredcommunication unit 13, a control unit 14, a control plane unit 15, aPDCCH control unit 16, a data plane unit 17, and an RAR control unit 18.

The radio communication unit 11 is a radio interface which performsradio communication with the mobile station 20 and the relay station 30.The radio communication unit 11 subjects a radio signal received fromthe mobile station 20 or the relay station 30 to signal processingincluding demodulation and decoding, and extracts user data and controldata. In addition, the radio communication unit 11 subjects user dataand control data to be transmitted to the mobile station 20 or the relaystation 30 to signal processing including modulation and coding forradio transmission.

According to the instruction from the control unit 14, the scheduler 12performs the allocation (scheduling) of radio resources to the mobilestation 20 and the relay station 30. During the random access procedure,for example, the scheduler 12 allocates the UL radio resource to themobile station 20, and notifies the radio communication unit 11 of theallocated UL radio resource.

The wired communication unit 13 is a communication interface whichperforms wired communication with a host station. The wiredcommunication unit 13 receives user data to the mobile station 20 fromthe host station. Under the scheduling through the scheduler 12, thereceived user data is transferred to the mobile station 20. The wiredcommunication unit 13 further transfers the user data extracted by theradio communication unit 11 to the host station.

The control unit 14 controls processes of the radio communication unit11, the scheduler 12, and the wired communication unit 13. Within thecontrol unit 14, the control plane unit 15 and the data plane unit 17are provided. Within the control plane unit 15, the PDCCH control unit16 is provided. Within the data plane unit 17, the RAR control unit 18is provided.

The control plane unit 15 controls transmission and reception of controldata between the mobile station 20, the relay station 30, and its ownstation. Specifically, the control plane unit 15 acquires the controldata extracted by the radio communication unit 11 and performscommunication control according to the control data. The control planeunit 15 further notifies the radio communication unit 11 of the controldata to be transmitted to the mobile station 20 or the relay station 30.For example, the control plane unit 15 performs a process of an RRC(Radio Resource Control Protocol).

The PDCCH control unit 16 controls PDCCH signaling during the randomaccess procedure. Specifically, the PDCCH control unit 16 determineswhat information is included in the dedicated preamble notification(Msg0) to be transmitted to the mobile station 20 or the relay station30 by using the PDCCH. For example, the PDCCH control unit 16 may insertinto the Msg0 a CI of the component carrier in which the datacommunication is performed.

The data plane unit 17 controls transmission and reception of the userdata between the mobile station 20, the relay station 30, and its ownstation. For example, the data plane unit 17 performs processes of aPDCP (Packet Data Convergence Protocol), an RLC (Radio Link Control)protocol, and a MAC (Media Access Control) protocol.

The RAR control unit 18 controls MAC signaling during the random accessprocedure. Specifically, the RAR control unit 18 determines whatinformation is included in the random access response (Msg2) to betransmitted to the mobile station 20 or the relay station 30 by usingthe PDSCH. For example, the RAR control unit 18 may insert into the Msg2a CI of the component carrier in which the data communication isperformed.

FIG. 7 is a block diagram illustrating the mobile station. The mobilestation 20 has a radio communication unit 21, a cross carrier settingunit 22, a control unit 23, a control plane unit 24, a PDCCH controlunit 25, a data plane unit 26, and an RAR control unit 27.

The radio communication unit 21 is a radio interface which performsradio communication with the base station 10 and the relay station 30.The radio communication unit 21 subjects a radio signal received fromthe base station 10 or the relay station 30 to signal processingincluding demodulation and decoding, and extracts user data and controldata. In addition, the radio communication unit 21 subjects user dataand control data to be transmitted to the base station 10 or the relaystation 30 to signal processing including modulation and coding forradio transmission.

According to the instruction from the control unit 23, the cross carriersetting unit 22 performs setting of a frequency band (component carrier)in which the radio communication unit 21 performs signal processingduring the random access procedure. In the case where a CI is includedin the received Msg0 or Msg2, for example, the cross carrier settingunit 22 then sets the frequency band so as to perform the datacommunication by using the component carrier indicated by the CI. In thesecond embodiment, the CI is supposed to be inserted into the Msg0.

The control unit 23 controls processes of the radio communication unit21 and the cross carrier setting unit 22. Within the control unit 23,the control plane unit 24 and the data plane unit 26 are provided.Within the control plane unit 24, the PDCCH control unit 25 is provided.Within the data plane unit 26, the RAR control unit 27 is provided.

The control plane unit 24 controls transmission and reception of controldata between the base station 10, the relay station 30, and its ownstation. Specifically, the control plane unit 24 acquires the controldata extracted by the radio communication unit 21 and performscommunication control according to the control data. The control planeunit 24 further notifies the radio communication unit 21 of the controldata to be transmitted to the base station 10 or the relay station 30.For example, the control plane unit 24 performs a process of an RRC.

The PDCCH control unit 25 controls PDCCH signaling during the randomaccess procedure. Specifically, the PDCCH control unit 25 analyzes theMsg0 to be received through the PDCCH from the base station 10 or therelay station 30, and performs a process based on the informationincluded in the Msg0. In the case where the CI is inserted into theMsg0, for example, the PDCCH control unit 25 performs receptionprocessing of the PDSCH by using the component carrier indicated by theCI. In the start of the reception processing, activation of thecomponent carrier and allocation of the buffer which stores the receiveduser data may be included.

The data plane unit 26 controls transmission and reception of the userdata between the base station 10, the relay station 30, and its ownstation. For example, the data plane unit 26 performs processes of thePDCH, RLC, and MAC.

The RAR control unit 27 controls MAC signaling during the random accessprocedure. Specifically, the RAR control unit 27 analyzes the Msg2 to bereceived through the PDSCH from the base station 10 or the relay station30, and performs a process based on the information included in theMsg2. In the case where the CI is inserted into the Msg2, for example,reception processing of the PDSCH is performed by the component carrierindicated by the CI.

Also in the relay station 30, a radio communication unit and a controlunit may be provided in the same manner as in the base station 10 andthe mobile station 20. In that case, with regard to the radiocommunication between the base station 10 and its own station, thecontrol unit of the relay station 30 performs the same process as thatof the control unit 23 of the mobile station 20. With regard to controlof the radio communication between the mobile station 20 and its ownstation, the control unit of the relay station 30 further performs thesame process as that of the control unit 14 of the base station 10.

FIG. 8 is a flowchart illustrating a process of the base stationaccording to the second embodiment. The process illustrated in FIG. 8includes the following steps:

(Step S111) The control unit 14 sets states of the CC#1 to #5 withrespect to the mobile station 20. Specifically, the control unit 14identifies the above-described “Configured but Deactivated CC”,“Configured and Activated CC”, and “PDSCH monitoring set”.

(Step S112) The control unit 14 determines whether to implement crosscarrier scheduling. Specifically, the control unit 14 determines whetherto perform the data communication except for the component carrier inwhich the dedicated preamble notification (Msg0) is transmitted. Thecontrol unit 14 determines whether to implement the cross carrierscheduling, for example, based on a size of data to be transmitted tothe mobile station 20 and communication quality of the component carrierin which the Msg0 is transmitted. If not, the process advances to stepS113. If so, the process proceeds to step S114.

(Step S113) The PDCCH control unit 16 sets 0b111 in a CI field (CIF)included in the Msg0. This binary digit string represents that datacommunication is performed by the component carrier in which the Msg0 istransmitted. In place of 0b111, the PDCCH control unit 16 may set the3-bit CI indicating the component carrier in which the Msg0 istransmitted. The process then proceeds to step S116.

(Step S114) From among the CC#1 to #5, the control unit 14 selects oneor a plurality of the component carriers in which the data communicationis performed except for the component carrier in which the Msg0 istransmitted. The control unit 14 selects the component carrier, forexample, based on a size of data to be transmitted to the mobile station20 or communication quality of the CC#1 to #5.

(Step S115) The PDCCH control unit 16 sets a 3-bit CIF indicating thecomponent carrier selected at step S114 in a CIF included in the Msg0.The PDCCH control unit 16 transmits the Msg0 for each component carrierselected at step S114.

(Step S116) The radio communication unit 11 transmits the Msg0 includingthe CIF set at step S113 or S115 to the mobile station 20 by using thecomponent carrier included in the “PDCCH monitoring set”. In the casewhere the plurality of the component carriers are selected at step S114,the radio communication unit 11 transmits a plurality of the Msg0 sets.The plurality of the Msg0 sets may be transmitted by the same radiotransmission unit (e.g., the same subframe), or dispersed into thedifferent radio transmission units (e.g., different subframes) fortransmission.

(Step S117) In the case where the component carrier notified by the Msg0is set as the “Configured but Deactivated CC” (de-active state), thecontrol unit 14 changes it into the “Configured and Activated CC”(active state). The radio communication unit 11 receives the randomaccess preamble (Msg1) from the mobile station 20 by using the componentcarrier notified by the Msg0.

(Step S118) The RAR control unit 18 generates the random access response(Msg2) not including the CIF. The radio communication unit 11 transmitsthe Msg2 to the mobile station 20 by using the component carrier inwhich the Msg1 is received. Then, the data communication is performed bythe component carrier in which the Msg1 and the Msg2 are transmitted andreceived.

FIG. 9 is a flowchart illustrating a process of the mobile stationaccording to the second embodiment. The process illustrated in FIG. 9includes the following steps:

(Step S121) The control unit 23 sets states of the CC#1 to #5.Specifically, the control unit 23 identifies the “Configured butDeactivated CC”, the “Configured and Activated CC”, and the “PDCCHmonitoring set”. The radio communication unit 21 monitors the PDCCH ofthe component carrier included in the “PDCCH monitoring set”.

(Step S122) The radio communication unit 21 receives the Msg0 from thebase station 10 by using the component carrier included in the “PDCCHmonitoring set”. The PDCCH control unit 25 extracts the CIF included inthe Msg0. In the case where the plurality of the Msg0 sets are received,the PDCCH control unit 25 extracts the CIF in each Msg0.

(Step S123) The PDCCH control unit 25 identifies the component carrierindicated by the CIF extracted at step S122, and performs receptionprocessing of the PDSCH by using the above component carrier. In thecase where the component carrier indicated by the CIF is set as the“Configured but Deactivated CC”, the PDCCH control unit 25 changes itinto the “Configured and Activated CC”. The cross carrier setting unit22 sets a frequency band for performing signal processing.

(Step S124) The radio communication unit 21 transmits the Msg1 using asignal sequence specified by the Msg0 to the base station 10 through thePRACH of the component carrier indicated by the CIF. In the case wherethe plurality of the Msg0 sets are received and the plurality of thecomponent carriers are identified at step S123, the radio communicationunit 21 transmits the Msg1 for each identified component carrier. Theradio communication unit 21 may transmit a plurality of the Msg1 sets atthe same timing or at the different timing.

(Step S125) The radio communication unit 21 receives the Msg2 from thebase station 10 by using the component carrier in which the Msg1 istransmitted. The RAR control unit 27 performs a process based oninformation included in the Msg2. The radio communication unit 21performs data communication by using the component carrier in which theMsg1 and the Msg2 are transmitted and received.

FIG. 10 illustrates a first random access example according to thesecond embodiment. Suppose here that the mobile station 20 sets the CC#1and #2 as the “Configured and Activated CC” and the CC#3 to #5 as the“Configured but Deactivated CC”. Suppose further that the “PDCCHmonitoring set” includes only the CC#1.

(Step S131) The base station 10 transmits the Msg0 including CIF=0b001to the mobile station 20 by using the CC#1 set as the “PDCCH monitoringset”.

(Step S132) The mobile station 20 transmits the Msg1 to the base station10 by using the CC#2 indicated by the CIF=0b001. Since the CC#2 is setas the “Configured and Activated CC”, the mobile station 20 need notchange a state of the CC#2.

(Step S133) The base station 10 transmits the Msg2 to the mobile station20 by using the CC#2 in which the Msg1 is received. For example, themobile station 20 then transmits data to the base station 10 by usingthe CC#2.

Transmission characteristics of radio signals are different in eachcomponent carrier (in each frequency band). Therefore, when the Msg1 andthe Msg2 are transmitted and received by the component carrier in whichthe data communication is performed, stabilization of the datacommunication is effectively attained. In addition, for ease ofexplanation of FIG. 10, only the CC#1 is set as the “PDCCH monitoringset” and further any CC may be also set as the “PDCCH monitoring set”.In this case, the Msg0 is transmitted by the CC set as the “PDCCHmonitoring set”.

FIG. 11 illustrates a second random access example according to thesecond embodiment. States of the CC#1 to #5 at the time of starting therandom access procedure are the same as those of FIG. 10.

(Step S141) The base station 10 transmits the Msg0 including CIF=0b010to the mobile station 20 by using the CC#1 set as the “PDCCH monitoringset”. Since the CC#3 indicated by the CIF=0b010 is set as the“Configured but Deactivated CC”, it is activated and changed into the“Configured and Activated CC”.

(Step S142) The mobile station 20 transmits the Msg1 to the base station10 by using the CC#3 indicated by the CIF=0b010. At this time, in thesame manner as in the base station 10, the mobile station 20 activatesthe CC#3 and changes it into the “Configured and Activated CC”.

(Step S143) The base station 10 transmits the Msg2 to the mobile station20 by using the CC#3 in which the Msg1 is received. For example, themobile station 20 then transmits data to the base station 10 by usingthe CC#3.

While performing a procedure for transmitting and receiving the Msg0 andthe Msg1, the base station 10 and the mobile station 20 change a stateof the CC#3. Specifically, the Msg0 and the Msg1 double as signaling forchanging a state of the CC#3. Accordingly, the base station 10 and themobile station 20 need not separately perform the signaling for changinga state of the CC#3.

FIG. 12 illustrates a third random access example according to thesecond embodiment. States of the CC#1 to #5 at the time of starting therandom access procedure are the same as those of FIG. 10.

(Step S151) The base station 10 transmits the Msg0 including theCIF=0b001 to the mobile station 20 by using the CC#1 set as the “PDCCHmonitoring set”.

(Step S152) The base station 10 transmits the Msg0 including theCIF=0b010 to the mobile station 20 by using the CC#1. Since the CC#3indicated by the CIF=0b010 is set as the “Configured but DeactivatedCC”, the base station 10 activates the CC#3 and changes it into the“Configured and Activated CC”. The base station 10 may further transmittwo Msg0 sets at the same timing.

(Step S153) The mobile station 20 transmits the Msg1 to the base station10 by using CC#2 indicated by the CIF=0b001.

(Step S154) The mobile station 20 transmits the Msg1 to the base station10 by using the CC#3 indicated by the CIF=0b010. At this time, in thesame manner as in the base station 10, the mobile station 20 activatesthe CC#3 and changes it into the “Configured and Activated CC”. Themobile station 20 may further transmit two Msg1 sets at the same timing.

(Step S155) By using the CC#2, the base station 10 receives the Msg1 andtransmits the Msg2 to the mobile station 20. By using the CC#2, forexample, the mobile station 20 then transmits data to the base station10.

(Step S156) By using the CC#3, the base station 10 receives the Msg1 andtransmits the Msg2 to the mobile station 20. By using the CC#3, forexample, the mobile station 20 then transmits data to the base station10.

The signal sequence specified by the Msg0 transmitted at step S151 andthe signal sequence specified by the Msg0 transmitted at step S152 maybe the same or different from each other. Specifically, with respect tothe Msg1 transmitted at step S153 and the Msg1 transmitted at step S154,the mobile station 20 may use the same signal sequence or differentsignal sequence.

In the above-described example of the cross carrier scheduling, the basestation 10 is supposed to recognize states of the CC#1 to #5 of themobile station 20. In the case where the base station 10 or the mobilestation 20 has a reason that some of the component carriers among theCC#1 to #5 are unusable, the base station 10 excludes such a componentcarrier and selects the component carrier in which the datacommunication is performed. The above-described cross carrier schedulingis implemented, for example, at the time when the mobile station 20performs random access to the base station 10 from a state of theconnected mode or idle mode.

FIG. 13 illustrates a first format example of the Msg0. The Msg0 is acontrol message to be transmitted through the PDCCH. As a field, theMsg0 includes Flag, Local/Dist, Resource Block Assignment, PreambleIndex, PRACH Mask Index, Carrier Indicator, and CRC. A bit length of theResource Block Assignment field is different depending on a DL bandwidthof the component carrier. FIG. 13 illustrates a bandwidth by using thenumber of RBs (resource blocks). Here, 100 RBs are equal to a 20 MHzwidth.

Fields except the Carrier Indicator field are described, for example, in“Evolved Universal Terrestrial Radio Access (E-UTRA); Multiplexing andchannel coding” (3GPP, TS 36.212 V9.0.0, 2009-12). In the secondembodiment, the Flag is fixed to 1, the Local/Dist is fixed to 0, andall of the Resource Block Assignment sets are fixed to 1. When a fixedbit is inserted to lengthen the Msg0, accuracy of the error detection isimproved. The Preamble Index indicates information for specifying thesignal sequence used for the Msg1. The PRACH Mask Index indicatesinformation used for transmitting the Msg1. The CRC indicates a parityused for the error detection of the Msg0.

As described above, the Carrier Indicator indicates a 3-bit binary bitstring for specifying the component carrier in which the datatransmission is performed. In an example of FIG. 13, the CarrierIndicator field is inserted between the PRACH Mask Index field and theCRC field. In the above-described literatures “Evolved UniversalTerrestrial Radio Access (E-UTRA); and Multiplexing and channel coding”,there is described a format on which the Padding field is providedbetween the PRACH Mask Index field and the CRC field.

FIG. 14 illustrates a second format example of the Msg0. In the formatexample of FIG. 14, most significant 3 bits of the binary bit stringallocated to the Resource Block Assignment field in the format exampleof FIG. 13 is allocated to the Carrier Indicator field. Specifically,the Carrier Indicator field is inserted between the Local/Dist field andthe Resource Block Assignment field. The Padding field is providedbetween the PRACH Mask Index field and the CRC field. All the Paddingsets are fixed to 1.

FIG. 15 illustrates a third format example of the Msg0. In the formatexample of FIG. 15, least significant 3 bits of the binary bit stringallocated to the Resource Block Assignment field in the format exampleof FIG. 13 is allocated to the Carrier Indicator field. Specifically,the Carrier Indicator field is inserted between the Resource BlockAssignment field and the Preamble index field.

In addition to format examples of FIGS. 14 and 15, there is alsoconsidered a method in which intermediate significant 3 bits of thebinary digit string allocated to the resource block assignment field ofthe format example of FIG. 13 are allocated to the carrier indicatorfield.

Incidentally, in the format example, a data length of the Msg0 isdifferent depending on a DL bandwidth of the component carrier.Therefore, a plurality of the Msg0 sets having different data lengthsmay be transmitted by the CC#1. Suppose, for example, that a DLbandwidth of the CC#2 is 20 MHz and a DL bandwidth of the CC#3 is 10MHz. In this case, the Msg0 corresponding to the CC#2 and the Msg0corresponding to the CC#3 have different data lengths.

On the other hand, the mobile station 20 blind-decodes the PDCCH andextracts the Msg0. Accordingly, for reducing an overhead of the blinddecoding, the mobile station 20 preferably adjusts a size so that a sizeof the Msg0 may be constant even if the DL bandwidth is differentdepending on the component carrier. Further, for facilitating theextraction of the CIF, the mobile station 20 preferably makes constant aposition of the CIF in the entire Msg0.

FIG. 16 illustrates a first size adjustment example of the Msg0. Thesize adjustment example of FIG. 16 corresponds to the format exampleillustrated in FIG. 13. In this size adjustment example, the PADDINGfield having a length according to the DL bandwidth is inserted betweenthe Resource block Assignment field and the Preamble Index field.Through the process, a size of the Msg0 becomes constant withoutrelation to the DL bandwidth. Since a position of the CIF is constant,after the decoding of the Msg0, the CIF is easily extracted to identifythe component carrier to be used. Further, since positions of thePreamble Index field and the PRACH Mask Index field are constant, theMsg1 is easily generated with reference to the above fields.

FIG. 17 illustrates a second size adjustment example of the Msg0. Thesize adjustment example of FIG. 17 corresponds to the format exampleillustrated in FIG. 14. In the same manner as in the size adjustmentexample of FIG. 16, the PADDING field having a length according to theDL bandwidth is inserted between the Resource block Assignment field andthe Preamble Index field. Through the process, a size of the Msg0becomes constant, and at the same time a position of the CIF becomesconstant without relation to the DL bandwidth. Positions of the PreambleIndex field and the PRACH Mask Index field further become constant.

FIG. 18 illustrates a third size adjustment example of the Msg0. Thesize adjustment example of FIG. 18 corresponds to the format exampleillustrated in FIG. 15. In this size adjustment example, the PADDINGfield having a length according to the DL bandwidth is inserted betweenthe Local/Dist field and the Resource Block Assignment field. Throughthe process, a size of the Msg0 becomes constant, and at the same time aposition of the CIF becomes constant without relation to the DLbandwidth. Positions of the Preamble Index field and the PRACH MaskIndex field further become constant.

According to this mobile communication system of the second embodiment,by transmitting the Msg0 to the mobile station 20, the base station 10gives to the mobile station 20 the use permission of the componentcarriers except the component carrier in which the Msg0 is transmitted.In other words, the base station 10 implements the cross carrierscheduling by using the Msg0. Accordingly, the base station 10 and themobile station 20 need not separately perform a procedure of the usepermission of the component carrier.

The base station 10 and the mobile station 20 further change thecomponent carrier in a de-active state into that in an active statealong with the transmission and reception of the Msg0 and the Msg1.Accordingly, the base station 10 and the mobile station 20 need notseparately perform a procedure of the state change of the componentcarrier. As can be seen from the above description, the base station 10and the mobile station 20 effectively perform use control of theplurality of the component carriers.

Third Embodiment

Next, a third embodiment will be described. The third embodiment will bedescribed with a focus on a difference from the above-described secondembodiment, and the same matters will not be repeated. In the secondembodiment, the cross carrier scheduling is implemented by the Msg0, andon the other hand the cross carrier scheduling is implemented by theMsg2 in the third embodiment.

A mobile communication system according to the third embodiment isimplemented by the same system configuration as that of the mobilecommunication system according to the second embodiment illustrated inFIG. 2. A base station and mobile station of the third embodiment areimplemented by the same block configurations as those of the basestation 10 and mobile station 20 of the second embodiment illustrated inFIGS. 6 and 7. The third embodiment will be described below by usingreference numerals used in FIGS. 2, 6, and 7.

FIG. 19 is a flowchart illustrating a process of the base stationaccording to the third embodiment. The process illustrated in FIG. 19includes the following steps:

(Step S211) The control unit 14 sets states of the CC#1 to #5 withregard to the mobile station 20. Specifically, the control unit 14identifies the above-described “Configured but Deactivated CC”,“Configured and Activated CC”, and “PDCCH monitoring set”.

(Step S212) The PDCCH control unit 16 generates the dedicated preamblenotification (Msg0) not including the CIF. The radio communication unit11 transmits the Msg0 to the mobile station 20 by using the componentcarrier included in the “PDCCH monitoring set.

(Step S213) The radio communication unit 11 receives the random accesspreamble (Msg1) from the mobile station 20 by using the componentcarrier in which the Msg0 is transmitted.

(Step S214) The control unit 14 determines whether to implement thecross carrier scheduling. Specifically, the control unit 14 determineswhether to perform the data communication except for the componentcarrier in which the random access response (Msg2) is transmitted. Ifnot, the process advances to step S215. If so, the process proceeds tostep S216.

(Step S215) The RAR control unit 18 sets the 0b111 in the CIF includedin the Msg2. This binary digit string indicates that the datacommunication is performed by the component carrier in which the Msg2 istransmitted. The process then proceeds to step S218.

(Step S216) From among the CC#1 to #5, the control unit 14 selects oneor a plurality of component carriers in which the data communication isperformed, except for the component carrier in which the Msg2 istransmitted.

(Step S217) The RAR control unit 18 sets a 3-bit CIF indicating thecomponent carrier selected at step S216. Note that the Msg2 istransmitted for each component carrier selected at step S216.

(Step S218) The radio communication unit 11 transmits the Msg2 includingthe CIF set at step S215 or S217 to the mobile station 20 by using thecomponent carrier included in the “PDCCH monitoring set. In the casewhere the plurality of the component carriers are selected at step S216,the radio communication unit 11 transmits a plurality of the Msg2 sets.In the case where the component carrier notified by the Msg2 is set asthe “Configured but Deactivated CC” (de-active state), the control unit14 changes it into the “Configured and Activated CC” (active state). Theradio communication unit 11 then performs the data communication byusing the component carrier notified by the Msg2.

FIG. 20 is a flowchart illustrating a process of the mobile stationaccording to the third embodiment. The process illustrated in FIG. 20includes the following steps:

(Step S221) The control unit 23 sets states of the CC#1 to #5.Specifically, the control unit 23 identifies the “Configured butDeactivated CC”, the “Configured and Activated CC”, and the “PDCCHmonitoring set”. The radio communication unit 21 monitors the PDCCH ofthe component carrier included in the “PDCCH monitoring set”.

(Step S222) The radio communication unit 21 receives the Msg0 notincluding the CIF from the base station 10 by using the componentcarrier included in the “PDCCH monitoring set”.

(Step S223) The radio communication unit 21 transmits the Msg1 using thesignal sequence specified by the Msg0 to the base station 10 by usingthe PRACH of the component carrier in which the Msg0 is transmitted.

(Step S224) The radio communication unit 21 receives the Msg2 from thebase station 10 by using the component carrier in which the Msg1 istransmitted. The RAR control unit 27 extracts the CIF included in theMsg2. In the case where the plurality of the Msg2 sets are received, theRAR control unit 27 extracts the CIF for each Msg2.

(Step S225) The RAR control unit 27 identifies one or the plurality ofthe component carriers indicated by the CIF extracted at step S224, andperforms reception processing of the PDSCH by using the componentcarriers. In the case where the component carrier indicated by the CIFis set as the “Configured but Deactivated CC”, the RAR control unit 27changes it into the “Configured and Activated CC”. The cross carriersetting unit 22 sets a frequency band for performing signal processing.

(Step S226) The radio communication unit 21 performs data communicationby using the component carrier identified at step S225.

FIG. 21 illustrates a first random access example according to the thirdembodiment. Suppose here that the mobile station 20 sets the CC#1 and #2as the “Configured and Activated CC” and the CC#3 to #5 as the“Configured but Deactivated CC”. Suppose further that the “PDCCHmonitoring set” includes only the CC#1.

(Step S231) The base station 10 transmits the Msg0 to the mobile station20 by using the CC#1 set as the “PDCCH monitoring set”.

(Step S232) The mobile station 20 transmits the Msg1 to the base station10 by using the CC#1 in which the Msg0 is received.

(Step S233) The base station 10 transmits the Msg2 including theCIF=0b001 to the mobile station 20 by using the CC#1 in which the Msg1is received. In the Msg2, timing adjustment information on the ULfrequency band of the CC#2 is included.

(Step S234) By using the CC#2 indicated by the CIF=0b001, for example,the mobile station 20 transmits data to the base station 10. Note thatsince the CC#2 is set as the “Configured and Activated CC”, the mobilestation 20 need not change a state of the CC#2.

FIG. 22 illustrates a second random access example according to thethird embodiment. The states of the CC#1 to #5 at the time of startingthe random access procedure are the same as those of FIG. 21.

(Step S241) The base station 10 transmits the Msg0 to the mobile station20 by using the CC#1 set as the “PDCCH monitoring set”.

(Step S242) The mobile station 20 transmits the Msg1 to the base station10 by using the CC#1 in which the Msg0 is received.

(Step S243) The base station 10 transmits the Msg2 including theCIF=0b010 to the mobile station 20 by using the CC#1 in which the Msg1is received. Since the CC#3 indicated by the CIF=0b010 is set as the“Configured but Deactivated CC”, the base station 10 activates the CC#3and changes it into the “Configured and Activated CC”. Note that in theMsg2, the timing adjustment information on the UL frequency band of theCC#3 is included.

(Step S244) By using the CC#3 indicated by the CIF=0b010, for example,the mobile station 20 transmits data to the base station 10. At thistime, in the same manner as in the base station 10, the mobile station20 activates the CC#3 and changes the “Configured but Deactivated CC”into the “Configured and Activated CC”.

FIG. 23 illustrates a third random access example according to the thirdembodiment. The states of the CC#1 to #5 at the time of starting therandom access procedure are the same as those of FIG. 21.

(Step S251) The base station 10 transmits the Msg0 to the mobile station20 by using the CC#1 set as the “PDCCH monitoring set”.

(Step S252) The mobile station 20 transmits the Msg1 to the base station10 by using the CC#1 in which the Msg0 is received.

(Step S253) The base station 10 transmits the Msg2 including theCIF=0b001 to the mobile station 20 by using the CC#1 in which the Msg1is received. Note that in the Msg2, the timing adjustment information onthe UL frequency band of the CC#2 is included.

(Step S254) The base station 10 transmits the Msg2 including theCIF=0b010 to the mobile station 20 by using the CC#1 in which the Msg1is received. Since the CC#3 indicated by the CIF=0b010 is set as the“Configured but Deactivated CC”, the base station 10 activates the CC#3and changes it into the “Configured and Activated CC”. Note that in theMsg2, the timing adjustment information on the UL frequency band of theCC#3 is included.

(Step S255) By using the CC#2 indicated by the CIF=0b001, for example,the mobile station 20 transmits data to the base station 10.

(Step S256) By using the CC#3 indicated by the CIF=0b010, for example,the mobile station 20 transmits data to the base station 10. At thistime, in the same manner as in the base station 10, the mobile station20 activates the CC#3 and changes the “Configured but Deactivated CC”into the “Configured and Activated CC”.

FIG. 24 illustrates a first format example of the Msg2. In the formatexample of FIG. 24, the Msg2 includes a Carrier Indicator of 3 bits, aTiming Advance Command of 6 bits, a UL grant of 20 bits, and a TemporaryC-RNTI of 16 bits.

As described above, the carrier indicator is a value for discriminatingthe component carrier in which the data transmission is performed. TheTiming Advance Command is a value indicating an amount of the timingadjustment at the time of allowing the mobile station 20 to correct theUL transmission timing. The UL grant is information illustrating the ULradio resource allocated to the mobile station 20. The Temporary C-RNTIis an identifier dynamically allocated to the mobile station 20 throughthe base station 10. In addition, the Timing Advance Command indicatesthe amount of timing adjustment relating to the component carrierindicated by the Carrier Indicator. Accordingly, the mobile station 20adjusts the UL transmission timing after the random access procedure byusing the Timing Advance Command.

Here, the Timing Advance Command is described, for example, in “EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical layer procedures”(3GPP TS 36.213 V9.0.1, 2009-12).

In the above-described literature, two types of an absolute value in adisplacement of the timing and a relative value using as a reference thecurrently corrected timing are defined as the Timing Advance Command.The absolute value is used in the case where the Timing Advance Commandis first notified, or a validity period of a previously notified TimingAdvance Command is expired. The relative value is used in the case wherethe validity period of the previously notified Timing Advance Command isnot expired. The absolute value is represented by 11 bits and therelative value is represented by 6 bits. In the format example of FIG.24, the relative value is supposed to be used.

In the above format example, a most significant reserved bit is set toone. A most significant R bit of the Msg2 not including the CIF is setto zero. Through the process, the mobile station 20 easily determineswhether the Msg2 includes the CIF.

FIG. 25 illustrates a second format example of the Msg2. In the formatexample of FIG. 25, the Msg2 includes the Timing Advance Command of 11bits, the UL grant of 20 bits, the Carrier Indicator of 3 bits, and theTemporary C-RNTI of 13 bits. In the case of this format example, theabsolute value may be used as the Timing Advance Command. On the otherhand, the Temporary C-RNTI is smaller by 3 bits than that in the case ofFIG. 24. The base station 10 allocates an identifier capable of beingrepresented by 13 bits or less to the mobile station 20.

FIG. 26 illustrates a third format example of the Msg2. In the formatexample of FIG. 26, the Msg2 includes the Timing Advance Command of 11bits, the UL grant of 20 bits, the Temporary C-RNTI of 16 bits, and theCarrier Indicator of 3 bits. In the case of this format example, theabsolute value may be used as the Timing Advance Command. The basestation 10 allocates an identifier having a value larger than that ofFIG. 25 to the mobile station 20. Note that a size of the Msg2 increasesmore than those of the format examples of FIGS. 24 and 25. In addition,the CIF may be provided on the least significant bits in FIG. 26, andfurther the CIF may be inserted into the other positions.

According to this mobile communication system of the third embodiment,by transmitting the Msg2 to the mobile station 20, the base station 10gives to the mobile station 20 a use permission of the componentcarriers except the component carrier in which the Msg2 is transmitted.In short, the base station 10 implements the cross carrier scheduling byusing the Msg2. Accordingly, the base station 10 and the mobile station20 need not separately perform a procedure for the use permission of thecomponent carrier.

The base station 10 and the mobile station 20 further change thecomponent carrier in a de-active state into that in an active statealong with transmission and reception of the Msg2. Therefore, the basestation 10 and the mobile station 20 need not separately perform aprocedure for a state change in the component carrier. As can be seenfrom the above description, the base station 10 and the mobile station20 effectively perform use control of the plurality of the componentcarriers in the same manner as in the second embodiment.

Fourth Embodiment

Next, a fourth embodiment will be described. The fourth embodiment willbe described with a focus on a difference from the above-describedsecond and third embodiments, and the same matters will not be repeated.In the fourth embodiment, the cross carrier scheduling is implemented bythe Msg2 in the same manner as in the third embodiment. Note that thenon-contention based random access is supposed in the third embodiment,and on the other hand the contention based random access is supposed inthe fourth embodiment.

A mobile communication system according to the fourth embodiment isimplemented by the same system configuration as that of the mobilecommunication system according to the second embodiment illustrated inFIG. 2. A base station and mobile station according to the fourthembodiment are further implemented by the same block configuration asthose of the base station 10 and mobile station 20 of the secondembodiment illustrated in FIGS. 6 and 7. Hereinafter, the fourthembodiment will be described by using reference numerals used in FIGS.2, 6, and 7.

FIG. 27 is a flowchart illustrating a process of the base stationaccording to the fourth embodiment. The process illustrated in FIG. 27includes the following steps:

(Step S311) The control unit 14 sets states of the CC#1 to #5 withregard to the mobile station 20. Specifically, the control unit 14identifies the above-described “Configured but Deactivated CC”,“Configured and Activated CC”, and “PDCCH monitoring set”.

(Step S312) The radio communication unit 11 receives the random accesspreamble (Msg1) from the mobile station 20 by using the componentcarrier included in the “PDCCH monitoring set”. A signal sequence usedin the Msg1 is randomly selected by the mobile station 20.

(Step S313) The control unit 14 determines whether to implement thecross carrier scheduling. If not, the process advances to step S314. Ifso, the process proceeds to step S315.

(Step S314) The RAR control unit 18 sets the 0b111 as the CIF includedin the Msg2. The process then proceeds to step S317.

(Step S315) From among the CC#1 to #5, the control unit 14 selects oneor a plurality of component carriers in which the data communication isperformed, except for the component carrier in which the Msg2 istransmitted.

(Step S316) The RAR control unit 18 sets a 3-bit CIF indicating thecomponent carrier selected at step S315. In addition, the Msg2 istransmitted for each component carrier selected at step S315.

(Step S317) The radio communication unit 11 transmits the Msg2 includingthe CIF set at step S314 or S316 to the mobile station 20 by using thecomponent carrier in which the Msg1 is received. In the case where theplurality of the component carriers are selected at step S315, the radiocommunication unit 11 transmits a plurality of the Msg2 sets.

(Step S318) The radio communication unit 11 receives the Msg3 from themobile station 20 by using the component carrier notified by the Msg2.At this time, in the case where the component carrier notified by theMsg2 is set as the “Configured but Deactivated CC” (de-active state),the control unit 14 changes it into the “Configured and Activated CC”(active state).

(Step S319) The radio communication unit 11 transmits the Msg4 to themobile station 20 by using the component carrier in which the Msg3 isreceived. The radio communication unit 11 then performs datacommunication by using the component carrier in which the Msg3 and theMsg4 are transmitted and received.

FIG. 28 is a flowchart illustrating a process of the mobile stationaccording to the fourth embodiment. The process illustrated in FIG. 28includes the following steps:

(Step S321) The control unit 23 sets states of the CC#1 to #5.Specifically, the control unit 23 identifies the “Configured butDeactivated CC”, the “Configured and Activated CC”, and the “PDCCHmonitoring set”. The radio communication unit 21 monitors the PDCCH ofthe component carrier included in the “PDCCH monitoring set”.

(Step S322) The radio communication unit 21 transmits the Msg1 using therandomly selected signal sequence to the base station 10 by using thePRACH of the component carrier included in the “PDCCH monitoring set”.

(Step S323) The radio communication unit 21 receives the Msg2 from thebase station 10 by using the component carrier in which the Msg1 istransmitted. The RAR control unit 27 extracts the CIF included in theMsg2. In the case where the plurality of the Msg2 sets are received, theRAR control unit 27 extracts the CIF for each Msg2.

(Step S324) The RAR control unit 27 identifies one or the plurality ofthe component carriers indicated by the CIF extracted at step S323. Inthe case where the component carrier indicated by the CIF is set as the“Configured but Deactivated CC”, the RAR control unit 27 changes it intothe “Configured and Activated CC”. The cross carrier setting unit 22sets a frequency band for performing signal processing.

(Step S325) The radio communication unit 21 transmits the Msg3 to thebase station 10 by using the component carrier indicated by the CIF. Inthe case where the plurality of the Msg2 sets are received and theplurality of the component carriers are identified at step S324, theradio communication unit 21 transmits the Msg3 to the base station 10for each of the identified component carriers. The plurality of the Msg3sets may be transmitted at the same timing, or at different timing.

(Step S326) The radio communication unit 21 receives the Msg4 from thebase station 10 by using the component carrier in which the Msg3 istransmitted. The radio communication unit 21 then performs datacommunication by using the component carrier in which the Msg3 and theMsg4 are transmitted and received.

FIG. 29 illustrates a first random access example according to thefourth embodiment. Suppose here that the mobile station 20 sets CC#1 and#2 as the “Configured and Activated CC” and the CC#3 to #5 as the“Configured but Deactivated CC”. Suppose further that the “PDCCHmonitoring set” includes only the CC#1.

(Step S331) The mobile station 20 transmits the Msg1 using the randomlyselected signal sequence to the base station 10 by using the CC#1 set asthe “PDCCH monitoring set”.

(Step S332) The base station 10 transmits the Msg2 including theCIF=0b001 to the mobile station 20 by using the CC#1 in which the Msg1is received.

(Step S333) The mobile station 20 transmits the Msg3 to the base station10 by using the CC#2 indicated by the CIF=0b001.

(Step S334) The base station 10 transmits the Msg4 to the mobile station20 by using the CC#2 in which the Msg3 is received. By using the CC#2,for example, the mobile station 20 then transmits data to the basestation 10. Note that in the case where contention of the random accessoccurs, the mobile station 20 transmits the Msg1 to the base station 10again.

FIG. 30 illustrates a second random access example according to thefourth embodiment. States of the CC#1 to #5 at the time of starting therandom access procedure are the same as those of FIG. 29.

(Step S341) The mobile station 20 transmits the Msg1 using the randomlyselected signal sequence to the base station 10 by using the CC#1 set asthe “PDCCH monitoring set”.

(Step S342) The base station 10 transmits the Msg2 including theCIF=0b010 to the mobile station 20 by using the CC#1 in which the Msg1is received. Since the CC#3 indicated by the CIF=0b010 is set as the“Configured but Deactivated CC”, the base station 10 activates the CC#3and changes it into the “Configured and Activated CC”.

(Step S343) The mobile station 20 transmits the Msg3 to the base station10 by using the CC#3 indicated by the CIF=0b010. In the same manner asin the base station 10, the mobile station 20 activates the CC#3 andchanges the “Configured but Deactivated CC” into the “Configured andActivated CC”.

(Step S344) The base station 10 transmits the Msg4 to the mobile station20 by using the CC#3 in which the Msg3 is received. By using the CC#3,for example, the mobile station 20 then transmits data to the basestation 10.

FIG. 31 illustrates a third random access example according to thefourth embodiment. States of the CC#1 to #5 at the time of starting therandom access procedure are the same as those of FIG. 29.

(Step S351) The mobile station 20 transmits the Msg1 using the randomlyselected signal sequence to the base station 10 by using the CC#1 set asthe “PDCCH monitoring set”.

(Step S352) The base station 10 transmits the Msg2 including theCIF=0b001 to the mobile station 20 by using the CC#1 in which the Msg1is received.

(Step S353) The base station 10 transmits the Msg2 including theCIF=0b010 to the mobile station 20 by using the CC#1 in which the Msg1is received. Since the CC#3 indicated by the CIF=0b010 is set as the“Configured but Deactivated CC”, the base station 10 activates the CC#3and changes it into the “Configured and Activated CC”.

(Step S354) The mobile station 20 transmits the Msg3 to the base station10 by using the CC#2 indicated by the CIF=0b001.

(Step S355) The mobile station 20 transmits the Msg3 to the base station10 by using the CC#3 indicated by the CIF=0b010. At this time, in thesame manner as in the base station 10, the mobile station 20 activatesthe CC#3 and changes the “Configured but Deactivated CC” into the“Configured and Activated CC”.

(Step S356) The base station 10 transmits the Msg4 to the mobile station20 by using the CC#2 in which the Msg3 is received.

(Step S357) The base station 10 transmits the Msg4 to the mobile station20 by using the CC#3 in which the Msg3 is received.

As a format of the Msg2 according to the fourth embodiment, the formatexample described in the third embodiment is used. In the contentionbased random access, since there is a possibility that the base station10 does not recognize the mobile station 20 at the time of transmittingthe Msg2, there are preferably used formats as in FIGS. 25 and 26 inwhich the Timing Advance Command of an absolute value is transmitted. Inthe fourth embodiment, from the same reason, it is preferable that themobile station 20 may use all or the plurality of the predeterminedcomponent carriers.

Further, in the case of the contention based random access, it is alsoconsidered that the cross carrier scheduling is implemented for thepurpose of a load balancing so that a plurality of mobile stations donot intensely use a specific component carrier, distributing thecomponent carriers in which the random access procedure is performed tomitigate interference between cells, and distributing the componentcarriers in which the Msg3 is transmitted to reduce a contentionprobability.

According to the above-described mobile communication system of thefourth embodiment, the base station 10 implements the cross carrierscheduling by using the Msg2 in the same manner as in the thirdembodiment. Accordingly, a procedure of permission for the usage of thecomponent carrier need not be separately performed. Along with thetransmission and reception of the Msg2 and the Msg3, the base station 10and the mobile station 20 further change the component carrier in ade-active state into that in an activate state. Therefore, a procedureof the state change of the component carrier need not be separatelyperformed. As can be seen from the above discussion, the base station 10and the mobile station 20 effectively perform use control of theplurality of the component carriers in the same manner as in the secondand third embodiments.

According to the above-described radio communication apparatus, radiocommunication system, and radio communication method, use control of aplurality of frequency bands is effectively performed.

All examples and conditional language provided herein are intended forpedagogical purposes of aiding the reader in understanding the inventionand the concepts contributed by the inventor to further the art, and arenot to be construed as limitations to such specifically recited examplesand conditions, nor does the organization of such examples in thespecification relate to a showing of the superiority and inferiority ofthe invention. Although one or more embodiments of the present inventionhave been described in detail, it should be understood that variouschanges, substitutions, and alterations could be made hereto withoutdeparting from the spirit and scope of the invention.

What is claimed is:
 1. A radio communication apparatus to performcommunication with another radio communication apparatus by using aplurality of frequency bands, the radio communication apparatuscomprising: a receiving unit configured to receive, when performing arandom access procedure to said another radio communication apparatus, acontrol message by using a first frequency band as a response to apreamble message transmitted by the radio communication apparatus, thecontrol message instructing communication using a second frequency banddifferent from the first frequency band; and a control unit configuredto perform, when the control message corresponds to the preamblemessage, data communication with said another radio communicationapparatus by using the second frequency band.
 2. A radio communicationapparatus to perform communication with another radio communicationapparatus by using a plurality of frequency bands, the radiocommunication apparatus comprising: a control unit configured to selecta second frequency band different from a first frequency band, as afrequency band to be used for data communication by said another radiocommunication apparatus; and a transmitting unit configured to transmita control message to said another radio communication apparatus by usingthe first frequency band as a response to a preamble message receivedfrom said another radio communication apparatus when a random accessprocedure is performed, the control message instructing communicationusing the second frequency band selected by the control unit.
 3. A radiocommunication system to perform communication by using a plurality offrequency bands, the radio communication system comprising: a firstradio communication apparatus configured to transmit a control messageby using a first frequency band as a response to a preamble messagereceived by the first radio communication apparatus when a random accessprocedure is performed, the control message instructing communicationusing a second frequency band different from the first frequency; and asecond radio communication apparatus configured to receive the controlmessage from the first radio communication apparatus by using the firstfrequency band, and when the control message corresponds to the preamblemessage transmitted by the second radio communication apparatus, performdata communication by using the second frequency band.
 4. A radiocommunication method for use in a radio communication system includingfirst and second radio communication apparatuses to performcommunication by using a plurality of frequency bands, the radiocommunication method comprising: transmitting, by the first radiocommunication apparatus, a control message to the second radiocommunication apparatus by using a first frequency band as a response toa preamble message received from the second radio communicationapparatus when a random access procedure is performed by the secondradio communication apparatus, the control message instructingcommunication using a second frequency band different from the firstfrequency band; receiving, by the second radio communication apparatus,the control message from the first radio communication apparatus byusing the first frequency band; and performing, by the second radiocommunication apparatus, data communication by using the secondfrequency band when the control message corresponds to the preamblemessage.